This invention relates to an improved wheat milling process for converting wheat into a finely divided milled product such as flour and/or semolina, and to the improved milled wheat product produced thereby.
Conventionally, wheat is milled in roller mills which simultaneously (1) remove outer bran layers and germ from the wheat kernel or berry and (2) reduce the size of the starchy endosperm. A typical roller mill will include a sequence of counter-rotating opposed rollers which progressively break the wheat into smaller and smaller sizes. The output from each pair of rollers is sorted into multiple streams, typically by means of sifters and purifiers, to separate the bran and germ from the endosperm, and to direct coarser and finer fractions of the endosperm to appropriate rollers. Principles of Cereal Science and Technology, R. Carl Hoseney (The American Association of Cereal Chemists, Inc., 1986), describes the operation of a conventional roller mill at pages 139-143.
Such conventional roller mills reduce the size of the bran and germ simultaneously as they reduce the size of the endosperm. For this reason, the bran, germ and endosperm fragments are intimately mixed together, and portions of the endosperm inevitably remain with the bran and germ when the bran and germ are removed. This of course reduces milling efficiency and increases the cost of the final milled product.
Bran is also conventionally removed from cereal grains such as rice, barley and wheat by means of pearling machines. For example, Salete U.S. Pat. No. 3,960,068 and Salete-Garces U.S. Pat. Nos. 4,292,890 and 4,583,455 describe grain polishing and whitening machines which are indicated as being particularly suitable for polishing and whitening rice. These devices process dehusked rice to remove outer bran layers from the rice without breaking the endosperm by forcing the rice upwardly in an annular column between two sets of opposed abrasive elements. The inner set of abrasive elements rotates with respect to the outer, and rice in the region of the abrasive elements is fluidized by a radially outwardly directed air flow. Bran and removed flour from the rice pass radially outwardly and are thereby separated from the polished endosperm. Though pearling or polishing machines such as those described above are commonly used in processing rice and other cereal grains such as barley, they are not used in conjunction with roller milling operations of sound, milling quality wheat, to the best of applicant's knowledge.
Pearling has been used to improve the flour obtained from germinated wheat. See "A Technique to Improve Functionality of Flour from Sprouted Wheat," R. Liu, et al., Cereal Foods World, Vol. 31, No. 7, pp. 471-476 (July, 1986). This article describes a process for pearling germinated wheat or a blend of germinated and sound wheat in a Strong Scott Laboratory Barley Pearler before the pearled wheat is milled in a roller mill to produce flour. Pearling was used to remove damaged tissue resulting from germination, thereby improving flour quality. As discussed at page 474, pearling removed the germ from about one half of the germinated kernels but from only 3% of the sound kernels in a blend of germinated and sound wheat.
Wheat flour and semolina are milled in very large quantities, and any improvement in milling efficiency or in quality of the milled product will result in major cost savings.